Field of the Invention
The invention relates in some aspects to systems and methods for sympathetic neuromodulation, including cardiopulmonary sympathetic neuromodulation.
Description of the Related Art
Asthma is a common chronic airway disorder characterized by episodic reversible airflow obstruction, or asthma attacks, that are characterized by breathlessness, coughing, wheezing, and chest tightness. Airflow is obstructed by contraction of the smooth muscle surrounding the airway that is thought to be a result of airway hyperreactivity. Inflammation and increased mucous secretions are also thought to play a role in exacerbating the asthma attack. Exposures such as exercise, infection, allergens, chemicals, or airborne irritants may trigger an asthma attack. At this time, it is not clear how to prevent the development of asthma and there is no known cure. Pharmacologic methods to control the disease and prevent exacerbations are well-established and as a result symptomatic treatment has improved over the past 20 years.
Asthma prevalence is now at its highest level at over 8% of the population in United States. In 2010, an estimated 25.7 million people had asthma: 18.7 million adults aged 18 and over and 7 million children aged 0-17 years. As a result of the increasing prevalence of the disease, asthma has been a focus for public health action. The prevalence of asthma attacks among persons with asthma, although declining, remains above 50% and there are an estimated 46.7 million lost school, work and activity days per year. Asthma visits to the emergency department and hospitalizations were stable from 2001 to 2009 but death rates are declining from 2001 to 2009. There are approximately 2 million ED visits, 500,000 hospitalizations, and 10 million outpatient visits for asthma. Each day, this translates to approximately 40,000 unscheduled physician office visits, 5,000 emergency room visits, and 1,000 hospitalizations due to asthma. Predictors of death due to asthma include three or more ED visits in the past year, as asthma hospitalization or ED visit in the past month, overuse of short-acting beta agonists. There are approximately 4,000 deaths per year attributable to asthma and deaths occur at a rate of 3.3% per year. The care for asthma patients costs over $18 billion of healthcare resources each year. As a result of the better medications available to patients, they are living longer but with a higher overall cost to the healthcare system since there is no cure for the disease.
Asthma is classified as intermittent, mild persistent, moderate persistent, and severe persistent. Severe or treatment-resistant asthma is increasingly recognized as a major unmet clinical need. Asthma may also be classified as atopic (extrinsic) if symptoms are triggered by allergens (smoke, air pollution, pollen) or non-atopic. Asthma may also be classified exercise-induced, occupational or nocturnal. Poorly controlled severe asthma, called severe persistent asthma, constitutes about 5 to 10 percent of asthma patients in United States, or approximately 1 to 2 million patients. A new procedure has been developed for the treatment of these severe persistent asthmatic patients, called Alair bronchial thermoplasty. This is a bronchoscopic procedure in which a minimally-invasive radiofrequency catheter is delivered through a bronchoscope into the patients airways to directly ablate the smooth muscle lining the bronchi with the goal of reducing the contractions of these muscles. The procedure typically requires a total of three separate procedures separated by two to three weeks for up to one hour each under moderate sedation. The FDA approved the therapy in 2010 based on significant improvements in patients' quality of life after the procedure. Boston Scientific reported sales of $15-20 MM in 2010 and expected $40-50 MM in sales in 2013.
As a result a new treatment for asthma, as well as other diseases, is needed with the potential of cure. Ideally the treatment would be minimally invasive and require minimal, if any, hospital stay. The procedure would, in some cases, avoid direct disruption to bronchial tissue and should not necessitate inserting a bronchoscope directly into the hyperreactive airways in some embodiments. Ideally, the treatment could be performed in one or two outpatient or office visits under a local anesthetic. This is desirable for both pediatric and adult patients. The treatment can reduce or eliminate the need for chronic pharmaceutical therapy. Finally, the treatment may preferably be long lasting or permanent. The treatment can result in a significant cost reduction to the healthcare system by reducing medication consumption as well as outpatient, emergency department visits and hospitalizations each year.